This invention relates to well casing hangers, and more particularly to such hangers for use by the petroleum industry in wells under wide temperature range conditions.
As the petroleum industry continues to develop producing oil wells in increasingly severe environments, the requirements published by the American Petroleum Institute for safely controlling downhole pressures existent at the wellhead continue to become more demanding. Furthermore, the operating petroleum companies desire equipment which can be installed and sealed off as quickly and reliably as possible, and these requirements and preferences are difficult to satisfy with existing casing hangers. Effecting an annulus seal with an elastomeric seal element over wide temperature ranges, such as zero degrees F. to 275 degrees F., and minus 50 degrees F. to 180 degrees F., while supporting the suspended casing load has not been achieved with hangers prior to the present invention, usually because of the difficulty in allowing for the thermal expansion and contraction of the seal element which has a coefficient of thermal expansion about ten times greater than that of the steel elements of the hanger.
For maximum safety under the foregoing conditions the annulus seal should be effected automatically as soon as the casing load is hung off in the hanger, and excessive deformation of the casing, which would restrict the free bore drift of the casing, should be prevented. Also, when pressure is applied to the annulus the radial load on the slips should not increase. And, to further complicate the matter, the American Petroleum Institute has recently changed the allowable outside diameter tolerance for casing, thereby requiring hangers to operate with casing according to either revision of that Institute's specification number 5B.
The foregoing problems are solved, and the aforesaid requirements and preferences are satisfied, by a casing hanger embodying the present invention as described below and illustrated in the accompanying drawings.